This invention relates to the field of fire resistant fabrics, and more particularly to a coating composition and method for imparting both fire resistance and water-repellency to light weight low cost tentage fabric.
Fabrics such as tentage fabric are conventionally treated with various coatings or finishes to impart water-repellency. Such finishes are typically applied by continuously feeding a strip of the fabric under a knife blade in contact with the upper surface of the fabric and delivering either a solution of the coating material or a molten coating formulation to the surface of the fabric just ahead of the knife blade. The knife blade causes the coating material to become uniformly distributed in a thin film over substantially the entire upper surface of the fabric. A dry film is obtained by allowing the material to cool, where a molten formulation is used, or by drying where a solvent formulation is employed. In the case of solvent formulations, drying is normally accelerated by passing the freshly coated fabric through an oven.
Fire retardant finishes are applied to tentage fabric in substantially the same fashion as water-repellent finishes. Water-repellent finishes have heretofore been available which are low in cost and can be applied by knife-coating strips of fabric moving at high speed. However, the imparting of fire resistance to tentage fabric has been a more expensive proposition. Materials which provide both water-repellency and fire retardancy are known but have generally been characterized by both high formulation cost and high application cost. Essentially all of the previously known fire retardant formulations have been solvent based, water based, or plastisols and the heat load associated with the drying and/or curing of these formulations severely limits the speed at which the coating process can be conducted. Drying is accelerated by use of ovens, but oven drying adds to production cost, and even the maximum economically feasible oven drying capacity does not permit the realization of processing rates equivalent to those obtainable with a melt formulation system.
While the available technology for imparting fire retardance and water resistance is economically viable if not attractive for heavy and relatively expensive fabrics, its utilization is practically prohibitive in the case of lighter weight fabrics where the cost of a given type of finishing operation represents a significantly higher proportion of the total finished fabric cost than in the case of heavy fabrics. Because of their more open structure, moreover, it is more difficult to impart fire and water resistance to light weight fabrics than to heavier fabrics, and the need for economical fire retardant and water resistant treatment of the lighter tentage has remained substantially unfulfilled.
The provision of improved fire retardant and water-repellent finishes for tentage is complicated by the need for the fabric to satisfy a number of additional criteria. Thus, the finished material must be flexible, nonblocking, possess a good hand, and exhibit low crock. Moreover, the coating must not contain or release any agents which might tender or deteriorate the fabric over a period of time.